1. Technical Field
The technical field relates to an audio processing apparatus for processing an input sound, a sound pickup apparatus and an imaging apparatus having the audio processing apparatus.
2. Related Art
In recent years, a digital camera that can record not only a still image but also a moving image is spreading. At the time of recording a moving image, a sound as well as an image should be recorded, and thus a microphone for collecting sounds is provided to such a digital camera. A digital camera tends to be miniaturized, which causes a microphone for collecting sounds to be also miniaturized. The miniaturization of the microphone deteriorates sensitivity of the microphone, thereby reducing an S/N ratio.
A sound processing apparatus for executing various filter processes in order to improve a S/N ratio with respect to a sound signal is generally known. For example, JP04-119708A discloses a configuration which increases attenuation in a low frequency region when an input signal is small, and decreases attenuation in a low frequency region when the input signal is large, to result in a flat frequency characteristic. According to the audio processing apparatus described in JP04-119708A, a gain in a frequency region determined by a characteristic of a filter circuit changes according to a change in an input signal even at a signal level of which temporal variation is great, so that noises can be repressed without causing a time delay.
In a technique of JP04-119708A, a passing band characteristic of a filter is changed according to an input signal level. However, a user occasionally feels a sense of discomfort in audibility depending on a way of changing a passing band characteristic.
To solve the above problem, an audio processing apparatus is provided that can reduce a user's sense of discomfort in audibility and can simultaneously improve an S/N ratio of an input sound signal, and a sound pickup apparatus and an imaging apparatus having the voice processing apparatus are also provided.